1. Field of Invention
The present invention relates to an electrical connection box for use in a vehicle, especially a car and more particularly to an electrical connection box in which vertically stacked bus bars can be prevented from becoming electrically conductive to each other when water enters a casing accommodating the bus bars. The invention also relates to such a box when mounted in a vehicle, e.g. an automobile.
2. Description of Related Art
In this kind of electrical connection box, in order to prevent leakage of current between the bus bars as a result of water penetration from the upper part of the casing while a car is being cleaned, a drainage path for passing water to the lower part of the casing is formed between the periphery of a stack having bus bars and insulation plates and the inner side surface of the casing, to discharge water to the outside via a drainage hole formed at the lower part of the casing.
To discharge water that has not passed via a drainage hole 5a formed between the periphery of the stack and the inner side surface of the casing, but has penetrated into the interior of the stack along the upper surface of the insulation plates, a drainage construction shown in FIGS. 6 and 7 can be provided. FIG. 6 is disclosed in Laid-Open Japanese Utility Model Publication No. 3-48322. In this drainage construction, a drainage hole 3 is formed in an upper insulation plate 1A of the stack, which includes bus bars 2A, 2B, 2c and insulation plates 1A, 1B. A drainage cylinder 4 projects from the periphery of the drainage hole 3 to the bottom of the stack. Water that has penetrated into the electrical connection box falls through the drainage hole 3 and the interior of the drainage cylinder 4 to be discharged to the outside via the drainage hole 5a of the lower casing 5.
FIG. 6 also shows that the insulation plate 1B has a drainage cylinder similar to the drainage cylinder 4. In the above-described embodiment, the water on the upper surface of the upper insulation plate 1A can be discharged to the outside. However, as shown in FIG. 7--which shows insulation plates 1A, 1B, 1c and bus bars 2A, 2B, 2c--there is a possibility that water (d) which has passed from the inner side surface of the casing to the upper surface of insulation plates (e.g., 1B and 1c) below the upper insulation plate 1A, drops from the ends (i.e. the ends adjacent to the drainage cylinder 4 in FIG. 7) of the insulation plates 1B, 1c, surrounding the drainage cylinder 4 onto the insulation plates below or onto the bus bars below. For example, there is a possibility that water flows from the end of the intermediate insulation plate 1B onto the upper surface of the lower insulation plate 1c adjacent to the intermediate insulation plate 1B. Consequently, the bus bar 2B installed on the intermediate insulation plate 1B and the bus bar 2c installed on the lower insulation plate 1c can be made electrically conductive to each other through the water.